1. Technical Field
The present invention relates in general to an improved magnetic head slider fabrication process, and in particular to a method and apparatus for increasing uniformity of the air bearing surface (ABS) of a slider. Still more particularly, the present invention relates to a method and apparatus for improving the capacity of an ion beam grid to uniformly etch an ABS specimen.
2. Description of the Prior Art
Generally, a data access and storage system consists of one or more storage devices that store data on magnetic or optical storage media. For example, a magnetic storage device is known as a direct access storage device (DASD) or a hard disk drive (HDD) and includes one or more disks and a disk controller to manage local operations concerning the disks. Disks are rigid platters, typically made of aluminum alloy or a mixture of glass and ceramic, covered with a magnetic coating. Typically, two or three disks are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm).
The only other moving part within a typical HDD is the head stack assembly. Within most HDDs, one magnetic read/write head or slider is associated with each side of each platter and flies just above or below the platter=s surface. Each read/write head is mounted on a suspension to form a head gimbal assembly (HGA). The HGA is then attached to a semi-rigid arm apparatus that supports the entire head flying unit. Several semi-rigid arms may be combined to form a single armature unit.
Each read/write head scans the surface of a disk during a Aread@ or Awrite@ operation. The head and arm assembly is moved utilizing an actuator that is often a voice coil motor (VCM). The stator of a VCM is mounted to a base plate or casting on which the spindle is also mounted. The base casting is in turn mounted to a frame via a compliant suspension. When current is fed to the motor, the VCM develops force or torque that is substantially proportional to the applied current. The arm acceleration is therefore substantially proportional to the magnitude of the current. As the read/write head approaches a desired track, a reverse polarity signal is applied to the actuator, causing the signal to act as a brake, and ideally causing the read/write head to stop directly over the desired track.
In a typical magnetic head slider fabrication process, ion milling has been one of the more popular techniques to form an air bearing surface (ABS) on the slider. The ABS allows the slider to be flown very close to a disk in order to retrieve or rewrite information in the disk. With the increasing demand on storage density, fly height (i.e., the altitude that the slider flies at relative to the disk) has become the most critical parameter to differentiate drive performance. In order to have sufficient control of the fly height, the etch depth uniformity of the ABS must be improved beyond the present tooling capacity.
As graphically illustrated in FIG. 1, the etch depth uniformity of a specimen 11 is typically controlled by an ion beam etching device 13 via a grid 15 formed from a durable material such as molybdenum. Specimen 11 is rotated as shown on a table 17 about its center, or grid 15 is rotated relative to specimen 11. Grid 15 is mounted to a stationary ion beam gun 19 directly above specimen 11. Grid 15 has a large number of symmetrically spaced-apart holes 21 and voids 22 that are free of holes 21 (see FIG. 2). The center 23 of grid 15 is concentric with the center of specimen 11. As specimen 11 is rotated, ion gun 19 emits a large axially-directed beam 25 onto the upper surface of grid 15 such that a grid filters beam 25 and small ion beamlets 27 permeate each of holes 21 to etch specimen 11. Although it is possible to redesign the grid using complicated ion optics theories in order to enhance the etch depth uniformity of the ABS, this solution is difficult and relatively expensive. Thus, an improved apparatus and method for increasing the uniformity of ABS etching depth is needed.
A shaper for an ion beam gun is a thin, flat plate having a generally elongated, non-symmetrical profile with notches and tabs. The shaper is mounted flat to the surface of an ion beam grid having an array of holes. The shaper is oriented radially on the grid from its center to a perimeter of the grid and covers some of the holes in the grid. The grid is mounted to an ion beam gun above a specimen that is rotated beneath the ion beam gun. The large ion beam is filtered into smaller ion beamlets by the grid. The ion beamlets permeate the holes in the grid that are not covered by the shaper. The ion beamlets reach the specimen to etch it more uniformly than a grid that does not have a shaper. This phenomena is due to blockage of the higher ion beam density along the radial direction. The ion beamlets that ultimately arrive at the specimen are themselves more uniform and can produce the more uniform pattern on the specimen. The shaper may be further optimized for a particular grid via a trial-and-error process to even further refine the uniformity of etching depth.
The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the preferred embodiment of the present invention, taken in conjunction with the appended claims and the accompanying drawings.